Sending' error (Ox800CCC6F): Outgoing mail slow or not accepted

For about two weeks now, outgoing e-mail on my cox account has either been slow or would not go out at all. (During that time there were some occasional glitches regarding incoming mail, but that hasn't happened now for a few days.) Outgoing e-mail on other accounts goes out immediately without problem. The send receive error message which I received reads as follows: Sending' reported error (Ox800CCC6F): 'Your outgoing (SMTP) e-mail server has reported an internal error. If you continue to receive this message, contact your server administrator or Internet service provider (ISP). The server responded: 554 fed1rmimpo110.cox.net Cox connection refused from I have rebooted many times. Any fixes? Thanks in advance.